LAVA TUBE EXPLORATION ON MARS USING SHARAD RADARGRAMS AND HIGH-RESOLUTION DIGITAL TERRAIN MODELS

Lava tubes on Mars have the ability to protect astronauts from solar radiation, meteoroid impacts, night/day temperature fluctuations, dust storms and other surface hazards. They may also harbor microbial life in a protected environment. Lava tubes on Mars are similar to terrestrial lava tubes, forming from cooled lava flows, but are longer and wider.

This study combines high-resolution digital terrain models (DTMs) with SHARAD (SHAllow RADar) radargrams to identify and characterize lava tubes in the vicinity of Elysium Mons and Alba Mons (formerly Alba Patera). High-resolution DTMs are available from stereo pair images taken by the HiRISE camera onboard the Mars Reconnaissance Orbiter (MRO). These images provide elevation at a lateral resolution of 1-2 meters per pixel with approximately 25 cm elevation accuracy. Topographic profiles across collapsed lava tube segments provide estimates of the lava tube cross-section dimensions.

The MRO also deployed SHARAD, designed to image the upper 1 km of the Martian subsurface. SHARAD’s center frequency is 20 MHz with a 10 MHz bandwidth, emitting approximately 700 pulses per second. Estimated vertical resolution is about 15 m. Preliminary analysis of the SHARAD radargrams indicate numerous echoes in the vicinity of lava tubes, including prominent diffractions. The shape, spacing and pattern of these diffractions are presently being analyzed to map geometry of the uncollapsed segments of these tubes in a similar manner to how ground-penetrating radar is used to map caves on Earth.